Thermoplastic films for heat seaming roof sheeting and method for covering roofs

ABSTRACT

A laminate seam of flat rubber sheet material for roofing comprising two layers (10, 11) of the sheet material, at least one layer of which is uncured or cured, and one layer of a thermoplastic film (14) interposed between the overlapped edges (12, 13) of the two layers of sheeting material to form a seam without the use of an adhesive. A method for covering a roof comprises the steps of applying a thermoplastic film (14) to the edge (12) of at least one layer of a flat rubber sheet material (10); applying a second layer of flat rubber sheet material (11) overlapping the thermoplastic film and the edge of the first flat rubber sheet material; heating the overlapped area to a temperature slightly above the peak melt temperature of the thermoplastic film; and, seaming the overlapped area under sufficient heat and pressure to provide an acceptable seam without the use of an adhesive.

TECHNICAL FIELD

The present invention relates generally to sheeting material used forroofing. More particularly a thin thermoplastic film is provided forseaming together two reinforced or unreinforced rubber sheets comprisingethylene-propylene-diene (EPDM) terpolymers, ethylene-propylenecopolymers, or other similar olefin-type polymers, and mixtures thereof,as well as sheeting manufactured from butyl, neoprene, or otherpolymers, including polyvinyl chloride (PVC), chlorinated polyethylene(CPE), chlorosulfonated polyethylene and the like. The rubber sheets maybe sulfur cured or uncured, and scrim reinforced or not. A method isalso provided for covering roofs which includes the step of employingthe thin thermoplastic film of the present invention.

BACKGROUND OF THE INVENTION

Polymeric roof sheeting is used as single ply roofing membrane forcovering industrial and commercial flat roofs. Such membranes aregenerally applied to the roof surface in vulcanized or cured state.

Because of outstanding weathering resistance and flexibility, cured EPDMbased roof sheeting has rapidly gained acceptance. This materialnormally is prepared by vulcanizing the composition in the presence ofsulfur or sulfur containing compounds such as mercaptans. Our earlierU.S. Pat. No. 4,803,020 also teaches the use of radiation crosslinkingpromoters in an EPDM sheeting composition which can be cured by ionizingradiation.

Notwithstanding the usefulness of radiation curing and sulfur curing, adisadvantage of utilizing these elastomers is the lack of adhesion ofEPDM, especially cured EPDM, to itself. Besides being highly laborintensive, this is a serious problem also because, in applying EPDMsheets to a roof, it is usually necessary to splice the cured EPDMsheets together. This splice or seam area is subjected to both shortterm and long term stresses such as those caused by roof movement, heavywinds, freeze-thaw cycling and thermal cycling. Such stresses maymanifest themselves in shear forces or peel forces, i.e., the seam peelsback under severe stress conditions or may cause a partially open seam(often referred to as a fish-mouth condition) under less severeconditions.

In view of the foregoing problem, it has been necessary to utilize anadhesive to bond the cured EPDM sheets together. As will be evident fromthe above discussion, an adhesive for bonding cured EPDM elastomerroofing sheets together must meet a number of requirements which areextremely difficult to satisfy. Thus, the adhesive must providesufficient seam peel and shear strength to permit the splice formed bybonding the cured EPDM roofing sheets together to resist both the shortterm and long term stresses such as those discussed hereinabove.Moreover, the adhesive must be resistant to oxidation, hydrolysis andchemical attack from pooled water. Additionally, the adhesive mustprovide the important property often referred to in the adhesive art as"Quick Stick". The term "Quick Stick" refers to that characteristic ofthe two sheets of material, which have been coated with an adhesivecomposition, to develop virtually immediate adhesive strength whenplaced in contact with each other.

Quick Stick is an extremely important property in an adhesive which isutilized to splice cured EPDM elastomer roofing sheets together. Thus,adhesive compositions presently known, generally require anywhere fromabout two (2) to about seven (7) days at room temperature (i.e. 22° C.)to attain maximum adhesive seam strength. At higher ambient temperature,this time period may be somewhat less but at a minimum it will generallybe at least 24 hours. The conventional procedure for splicing the EPDMroofing sheets together is to make the splice within a relatively shortperiod of time after the adhesive coating has been applied to eachsheet, generally within 30 minutes but often less. Accordingly, theadhesive composition must provide sufficient immediate adhesive strengthor Quick Stick to permit the splice to withstand stresses from winds,movement, handling by installers, etc. until the adhesive achieves itsmaximum strength which as indicated will generally take from about two(2) to seven (7) days.

Commercial contact adhesives which are conventionally employed forbonding cured EPDM elastomer roofing sheets together generally consistof solutions of neoprene or neoprene-type or butyl or butyl-typepolymers in aromatic or aromatic-aliphatic solvents containing2-butanone often along with tackifying resins. However, such adhesiveshave not proven to be very satisfactory due to their lower thandesirable seam peel adhesion strengths. Thus, the neoprene or butyl-typeadhesives often provide peel adhesion values at 22° C. of only 1 to 2pounds per linear inch. Additionally, the use of organic solvents insuch systems would likely run afoul of environmental regulations, andwhich control the release of volatile organics.

Pressure sensitive and contact adhesive compositions containingneutralized, partially neutralized or unneutralized sulfonateelastomers, tackifying resins and organic solvents or organic solventmixtures are known in the prior art as shown by U.S. Pat. No. 3,801,531and 3,867,247.

U.S. Pat. No. 3,801,531 relates to pressure sensitive adhesivecompositions which contain thiouronium derivatives of unsaturatedelastomers or neutralized, partially neutralized or unneutralizedsulfonated elastomers including sulfonated EPDM, tackifying resinsincluding phenol formaldehyde or alkylphenol formaldehyde resins andorganic solvents or organic solvent mixtures including a preferred 90:10mixture of toluene and isopropyl alcohol. However, the patent does notdisclose or suggest the use of alkylphenols or ethoxylated alkylphenolsin such compositions.

U.S. Pat. No. 3,867,247 relates to adhesive contact cements whichcontain neutralized, partially neutralized or unneutralized sulfonatedbutyl elastomers, tackifying resins including phenol formaldehyde oralkylphenol formaldehyde resins and organic solvents or organic solventmixtures including a preferred 90:10 mixture of toluene and isopropylalcohol. However, the patent does not disclose or suggest the use ofalkylphenols or ethoxylated alkylphenols in such compositions.

The adhesive compositions described in the aforementioned patents sufferfrom a significant disadvantage which materially limits their usefulnessas a contact adhesive for bonding cured EPDM elastomer roofing sheetstogether and that is their deficiency in Quick Stick properties. Alsothe use of organic solvents in such systems would likely run afoul ofenvironmental regulations, which control the release of volatileorganics.

One adhesive system for EPDM elastomers that provides good Quick Stickis described in U.S. Pat. No. 4,480,012, owned by the Assignee of recordherein. Such adhesives comprise a neutralized sulfonated EPDMelastomeric terpolymer; an organic hydrocarbon solvent; a para-alkylatedphenol formaldehyde tackifying resin and an alkylphenol or ethoxylatedalkylphenol. While the use of such adhesive compositions is an effectivemeans of joining and sealing the edges of elastomeric roofing material,if the use of adhesives could be eliminated, the additional labormaterial costs and related hardware necessary to apply the adhesivewould effect a significant cost savings. Moreover, elimination of theneed to cure the material prior to its application to a roof would alsobe advantageous.

Co-pending application U.S. patent application Ser. No. 07/594,461 nowU.S. Pat. No. 5,162,436 discloses a sheeting material composition whicheliminates the need for adhesives, solvents and the need for curingprior to application to the roof. While these advantages effect costsavings and are environmentally prudent, a need exists for providing aroof covering system which bonds quicker and results in a stronger bond.The high rate of bonding would also ensure that the roofing is watertight, an important requirement for most applications. A seam ofvariable width and hence strength is also desirable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermoplastic filmwhich replaces traditional adhesives for seaming together two reinforcedor unreinforced, cured or uncured EPDM or EPR roof sheeting materials.

It is another object of the present invention to provide a thermoplasticfilm for EPDM and EPR roof sheeting materials which eliminates the needfor a solvent or non-solvent based splicing adhesive and the relatedlabor and hardware necessary for mixing and application thereof.

It is still another object of the present invention to provide athermoplastic film for seaming together two EPDM, EPR or other olefintype roof sheeting materials, which do not necessarily require curingand which can be joined and seamed together at their edges without theuse of adhesives, either solvent or non-solvent based.

It is a further object of the present invention to provide athermoplastic film as described above which results in a water tight fitbetween the roof sheeting materials.

Yet another object of the present invention is to provide athermoplastic film as described above which eliminates the use oforganic solvents in seaming together EPDM or EPR roof sheetingmaterials.

It is still another object of the present invention to provide athermoplastic film as described above which can be used to form a seamof variable width and hence varied strength between two layers of EPDMor EPR roof sheeting.

In general the present invention relates to a laminate seam of flatrubber sheet material for roofing comprising two layers of sheetmaterial, at least one layer of which is uncured or cured; and one layerof a thermoplastic film interposed between the edge area of the twolayers of sheet material, when the edge areas are overlapped to form aseam without the use of an adhesive.

A method for covering a roof is also provided and comprises the steps ofapplying a thermoplastic film to the edge area of at least one layer ofa flat rubber sheet material; applying a second layer of flat rubbersheet material overlapping the thermoplastic film and the edge of thefirst flat rubber sheet material; heating the overlapped areas toslightly above the peak melt temperature of the thermoplastic film andseaming the overlapped areas using sufficient heat and pressure toprovide an acceptable seam without the use of an adhesive.

The roof sheeting used to practice this invention may also be sulfurcurable. Both uncured and cured roofing membranes may optionally bescrim reinforced.

At least one or more of the foregoing objects which shall becomeapparent to those skilled in the art are described in greater detailwith reference to the specification which follows.

BRIEF DESCRIPTION OF THE DRAWING

The drawing figure is a vertical cross-section of two single ply EPDMroofing membranes, joined at the seam area by a thermoplastic film,according to the present invention.

PREFERRED EMBODIMENT OF THE INVENTION

As noted, the sheeting materials used in the present invention compriseEPDM, EPR or other similar olefin type polymers. The term EPDM is usedin the sense of its definition as found in ASTM-D-1418-85 and isintended to mean a terpolymer of ethylene, propylene and a diene monomerwith the residual unsaturation portion of the diene in the side chain.Illustrative methods for preparing such terpolymers are found in U.S.Pat. No. 3,280,082, the disclosure of which is incorporated herein byreference. The preferred polymers having from about 60 to about 95weight percent ethylene and from about zero to about 12 weight percentof the diene with the balance of the polymer being propylene or someother similar olefin type polymer.

The diene monomer utilized in forming the EPDM terpolymer is preferablya non-conjugated diene. Illustrative examples of non-conjugated dieneswhich may be employed are dicyclopentadiene, alkyldicyclopentadiene,1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4-heptadiene,2-methyl-1,5-hexadiene, cyclooctadiene, 1,4-octadiene, 1,7-octadiene,5-ethylidene-2-norbornene, 5-n-propylidene-2-norbornene,5-(2-methyl-2-butenyl)-2-norbornene and the like. A typical EPDM isVistalon® MD-744 (Exxon Chemical Co.) a terpolymer having a MooneyViscosity (ML/4 at 125° C.) of about 52; an ethylene/propylene (E/P)ratio of 61/39 weight percent and 2.7 weight percent of unsaturation.

Particularly useful and preferred in preparing a sulfur curable EPDMcomposition is Royalene® 3180 (Uniroyal Chemical Co.) which has a MooneyViscosity (ML/4 at 125° C.) of about 54; an ethylene/propylene ratio ofabout 67/33 weight percent; about 2.2 weight percent of unsaturation(5-ethylidene-2-norbornene); about 2.7 percent by weight ofcrystallinity and a weight average molecular weight of approximately313,000 to 355,000. Vistalon® MD-744 (Exxon Chemical Co.) is anotheruseful sulfur curable EPDM rubber having a Mooney Viscosity (ML/4 at125° C.) of about 53; an ethylene/propylene (E/P) ratio of about 60/40weight percent; about 2.7 weight percent of unsaturation(5-ethylidene-2-norbornene) and a weight average of approximately360,000. Also useful are thermoplastic heat seamable sheeting materials,i.e., EPDM's and EPR's having a high degree of crystallinity as opposedto amorphous (non-crystalline) EPDM's or EPR's. Examples thereof includeRoyalene® 375 (Uniroyal Chemical Co.); and EPsyn® 5508 and EPsyn® MDE249 (Copolymer Rubber & Chemical Corporation). Royalene® 375 has aMooney Viscosity (ML/4 at 125° C.) of about 50.8; an E/P ratio of 75/25weight percent and about 2.0 weight percent of unsaturation(dicyclopentadiene) and a weight average molecular weight ofapproximately 190,000. EPsyn® 5508 has a Mooney Viscosity (ML/4 at 125°C.) of about 55.6; an E/P ratio of 73/27 weight percent and about 3.7weight percent of unsaturation. EPsyn® MDE 249, an experimentalterpolymer has a Mooney Viscosity (ML/4 at 125° C.) of about 56; an E/Pratio of 71/29 weight percent and about 1.7 weight percent ofunsaturation (5-ethylidene-2-norbornene) can also be employed. A morecomplete discussion of heat seamable materials, is set forth in ourcopending application, U.S. Ser. No. 07/594,457, the subject matter ofwhich is incorporated herein by reference.

The term EPR is used in the sense of its definition as found in ASTMD-1418-85 and is intended to mean a copolymer of ethylene and propylene.The preferred copolymers contain from about 30 to 95 weight percentethylene with the balance to total 100 weight percent being propylene. Atypical EPR is Vistalon® 719 (Exxon Chemical Co.) having an E/P ratio ofabout 75/25 weight percent.

Also, useful as a roofing material in the present invention is acopolymer of ethylene and butene. This particular copolymer has about 82weight percent ethylene with the balance to total 100 weight percentbeing butene. A typical ethylene/butene copolymer is GERS-1085 (UnionCarbide Corporation) having an Mw, as measured by GPC of at least about221,000. Other similar olefinic polymers (e.g., ethylene/octenecopolymer) can be used to practice this invention. Generally speakingany semi-crystalline polymer having more than about 2 percent by weightcrystallinity and selected from the group consisting of polyolefinsprepared from monomers containing at least 2 carbon atoms can beemployed. For purposes of discussion herein, references to EPDM, EPR orsimilar olefinic polymers is intended to include any of thesemi-crystalline polymers of the present invention.

The composition employed to form the sheeting material comprises 100parts by weight of EPDM, EPR, or other similar olefinic type polymers,including mixtures of two or more types, to which are added fillers andprocessing materials as well as optionally other components includingcuratives, all of which are discussed hereinbelow.

With respect first to the fillers, suitable fillers are selected fromthe group consisting of reinforcing and non-reinforcing materials, andmixtures thereof, as are customarily added to rubber. Examples includesuch materials as carbon black, ground coal, calcium carbonate, clay,silica, cryogenically ground rubber and the like. Preferred fillersinclude carbon black, ground coal and cryogenically ground rubber.

Carbon black is used in an amount of about 20 parts to about 300 partsper 100 parts of polymer (phr), preferably in an amount of about 60 toabout 150 phr. The preferred range of carbon black herein (60 to 150phr) is about equal to the amount of carbon black normally used inpreparing sulfur cured EPDM roof sheeting. The carbon black usefulherein is any carbon black. Preferred are furnace blacks such as GPF(general purpose furnace), FEF (fast extrusion furnace) and SRF(semi-reinforcing furnace).

The ground coal employed as a filler in the compositions of theinvention is a dry, finely divided black powder derived from a lowvolatile bituminous coal. The ground coal has a particle size rangingfrom a minimum of 0.26 microns to a maximum of 2.55 microns with theaverage particle size of 0.69±0.46 as determined on 50 particles, usingTransmission Electron Microscopy. The ground coal produces an aqueousslurry having a pH of about 7.0 when tested in accordance with ASTMD-1512. A preferred ground coal of this type is designated Austin Blackwhich has a specific gravity of 1.22±0.03, an ash content of 4.58% and asulfur content of 0.65%. Austin Black is commercially available fromCoal Fillers, Inc., P.O. Box 1063, Bluefield, Va. Amounts range fromabout 5 to 65 phr with about 15 to 35 being preferred.

Finally, essentially any cryogenically ground rubber may be employed asa filler in the composition of the invention. The preferredcryogenically ground rubbers are cryogenically ground EPDM, butyl,neoprene and the like. A preferred cryogenically ground rubber is acryogenically ground EPDM rubber. The preferred cryogenically groundEPDM rubber is a fine black rubbery powder having a specific gravity of1.129±0.015 and a particle size ranging from about 30 to about 300microns with an average particle size ranging from about 50 to about 80microns. Amounts range from about 5 to 40 phr with about 10 to 25 phrbeing preferred.

Mixtures of Austin black and cryogenically ground rubber useful hereinmay be utilized as a partial replacement for carbon black. Wheremixtures of these two fillers are employed the relative amounts thereofcan be widely varied; the overall total not exceeding about 60 phr. Theratio of Austin black to cryogenically ground rubber may range from adesired ratio of 2:1 to perhaps even a ratio of 3:1. Again, as notedhereinabove, other filler materials can be employed. Amounts of thesefiller materials fall within the range of amounts normally employed inpreparing sulfur cured conventional roof sheeting.

With respect to the processing material, it is included to improve theprocessing behavior of the composition (i.e. reduce mixing time andincrease rate of sheet forming and includes processing oils, waxes andthe like). The processing oil is included in an amount ranging fromabout 20 parts to about 150 parts process oil per 100 parts EPDMingredient phr, preferably in an amount ranging from about 60 to about100 phr. A preferred processing oil is a paraffinic oil, e.g. Sunpar2280 which is available from the Sun Oil Company. Other petroleumderived oils including naphthenic oils may be used.

Optional ingredients include, for example, other elastomers (e.g., butylelastomer, neutralized sulfonated EPDM, neutralized sulfonated butyl) inplace of minor amounts of the EPDM, secondary inorganic fillers (e.g.,talc, mica, clay, silicates, whiting) with total secondary fillercontent usually ranging from about 10 to about 150 phr, and conventionalamounts of other conventional agents, such as zinc oxide, stearic acid,antioxidants, antiozonants, flame retardants, and the like.

Regarding curatives, sulfur is preferred in amounts of about 0.3 to 2phr. As noted hereinabove, the roof sheeting compound is not cured priorto application and need not be cured subsequent thereto. The presence ofsulfur enhances bonding of the seams.

The compounding ingredients can be admixed, utilizing an internal mixer(such as a Banbury mixer), an extruder, and/or a two-roll mill, or othermixers suitable for forming a viscous relatively uniform admixture. Whenutilizing a type B Banbury internal mixer, in a preferred mode, the dryor powdery materials such as carbon black are added first followed bythe liquid process oil and finally the polymer (this type of mixing canbe referred to as an upside-down mixing technique).

The resulting admixture is sheeted to thickness ranging from 5 to 200mils, preferably from 35 to 60 mils, by conventional sheeting methods,for example, milling, calendering or extrusion. Preferably, theadmixture is sheeted to at least 40 gauge (0.040 inches) which is theminimum thickness specified in standards set by the Roofing Council ofthe Rubber Manufacturers Association for non-reinforced black EPDMrubber sheets for use in roofing applications. In many cases, theadmixture is sheeted to 40-45 gauge thickness since this is thethickness for a large percentage of "single-ply" roofing membranes usedcommercially. The sheeting can be cut to desired length and widthdimensions at this time.

The present invention is practiced by utilizing a thermoplastic filmbetween sheets of EPDM or EPR formed from materials as described herein.Once the first sheet is unrolled over the roof substructure in anotherwise conventional fashion, a thermoplastic film is applied to theedge or edges of the first sheet material in the seam area. The nextsheet is then applied onto the roof overlapping the thermoplastic filmto form a seam. The width of the seam can vary depending on therequirements specified by the architect, building contractor or roofingcontractor and thus, does not constitute a limitation of the presentinvention. Generally, seam widths can vary between about 1 to 6 inches.

With reference to the drawing figure, two layers of roofing membranesheet material, 10 and 11, are depicted with the edge area 12 of sheet10 being overlapped by the edge area 13 of sheet 11 to form a seam.Interposed between these overlapped edges, is a layer of thermoplasticfilm 14 which is employed according to the present invention to form theseam, without the use of adhesives.

The thin thermoplastic film of the present invention may comprise apolyolefin prepared from a monomer or monomers having from 2 to about 8carbon atoms, such as polyethylene, polypropylene, polybutene,polyoctene and the like, as well as ethylene-vinyl acetate copolymersand blends thereof. Generally, the thickness of the film can rangebetween from about 2 to about 20 mils although greater thicknesses maybe employed and thus, are not precluded. For testing purposes,polyethylene films were primarily employed.

Infrared spectrum of these liner films indicated the presence of onlyethylene monomer units. Mils of thickness and peak melt temperature (asdetermined using the Differential Scanning Calorimeter) for each of thethermoplastic materials are provided in Table I.

                  TABLE I                                                         ______________________________________                                        THERMOPLASTIC FILMS                                                                                         Tm. °C.                                  Seaming Material  Thickness (mils)                                                                          (by DSC)                                        ______________________________________                                        Red PE liner      3-4         108.7.sup.a                                     Transparent PE liner                                                                            3           111.8.sup.a                                     Embossed PE liner 4-5         109.4.sup.a                                     Pail liner-opaque.sup.b                                                                         15-18       130.5.sup.a                                     High MW Polyethylene sheeting                                                 P150.sup.c        6           139.4.sup.a                                     P550.sup.c        20          140.5.sup.a                                     ______________________________________                                         .sup.a Peak melt temperature                                                  .sup.b High density polyethylene                                              .sup.c STAMYLAN UH                                                       

Next, heat and some pressure are applied to the overlapped edges of tworoof sheets to form a seam. At the location of the seam, temperature isconveniently applied from about 100° to 550° C. using a Leisterhand-held heating gun and some pressure. Generally, the seam area shouldbe heated to slightly above the melt temperature of the thermoplasticfilm. Pressure can vary widely from a minimum of about 3 psi to as highas 60 psi, typically so long as it is adequate to provide an acceptable,water tight seam. Numerous techniques which utilize heat and somepressure can be used to produce a fully acceptable seam as are known tothose skilled in the art.

In order to demonstrate practice of the present invention, seams wereformed by bonding together layers of EPDM sheet material and variousthermoplastic films. These seams were prepared and subjected to bothpeel and shear adhesion tests, the results of which are provided inTables III and IV. The EPDM sheeting compositions employed for the testsare shown in Table II hereinbelow. The compositions exemplified aresubmitted for the purpose of further illustrating the nature of thepresent invention and are not to be considered as a limitation on thescope thereof. Parts and percentages are by weight, unless otherwiseindicated.

Compound Nos. 1 and 2 are typical EPDM polymers, which are not highlycrystalline. Compound No. 3 is a highly crystalline EPDM having greaterthan 2 percent crystallinity, derived from a high ethylene content, thatis, greater than 75 weight percent. We have found such EPDM and EPRpolymers to be useful as rooftop sheet material that is self-adheringi.e., no adhesive is required between overlapped layers to form theseam. Of course, the present invention can be employed with suchmaterials as well as more highly crystalline EPDM and EPR polymers whichdo require the use of an adhesive or thermoplastic films of the presentinvention. A more complete description of self-adhering rooftopmaterials is set forth in our copending application, U.S. Ser. No.07/594,457, the subject matter of which is incorporated herein.

                  TABLE II                                                        ______________________________________                                        SULFUR CURED AND UNCURED BLACK EPDM                                           SHEETING                                                                      Compound No.   (I)       (II)     (III)                                       ______________________________________                                        Royalene ® 3180                                                                          100       100      --                                          EPsyn ® MDE 249                                                                          --        --       100                                         HiStr GPF black                                                                              60        122      125                                         Hi-White ® R.sup.a                                                                       60        --       --                                          Austin Black   --        15       --                                          Paraffinic process oil                                                                       65        87       80                                          Zinc oxide     2.5       4        --                                          Stearic acid   1         1        --                                          Magnesium hydroxide                                                                          30        --       --                                          Cure Package   2.90      4.20     --                                          TOTAL          321.40    333.2    305                                         Specific gravity (calc.)                                                                     1.2748    1.1322   1.1099                                      Scrim Reinforcement                                                                          yes       no       yes                                         ______________________________________                                         .sup.a airfloated soft clay from J. M. Huber Corp.                       

Detailed Peel and Shear Adhesion Test Procedure

Each of the above rubber compounds was subjected to adhesion testingwhich necessitated the building of test pads comprising 6×6 inch sheets,some reinforced by a fiber reinforcement scrim, and some unreinforced,according to the following procedure:

1. A number of 6×6-inch rubber sheets approximately 45 mils(0.045-inches) in thickness were prepared using factory calenderedmembrane sheeting, some reinforced with a scrim fabric and someunreinforced. Some of these membranes were vulcanized with sulfur andsome were of the uncured variety.

2. A 6×6 inch sheet of the selected thermoplastic film was insertedbetween two 6×6 inch sheets of rubber.

3. Most of the rubber film assemblies were formed with a hand-heldLeister heating gun at 420° C. and 1.5-5 lbs pressure to the seamitself. Pressure was applied to the seam during the heating processusing a standard hand roller such as a 2 inch wide metal roller.

4. If the high MW polyethylene film was used either (P150 or P550), therubber/thermoplastic film assembly was then pressed using a positivepressure mold for about five minutes at 149° C.

5. A clicker machine with a one-inch wide die was utilized to prepare anumber of test specimens for seam peel (Type B, 90° peel) and shear(Type A, 180° peel) adhesion testing.

6. Testing machine: Model 1130 Instron Universal Tester--a testingmachine of the constant rate-of-jaw separation type. The machine wasequipped with suitable grips capable of clamping the specimens firmlyand without slippage throughout the tests.

7. The one-inch wide specimens were tested at the rate (both crossheadand chart speed) of two inches per minute using the adhesion test setforth in ASTM D-413 (machine method). Both peel and shear adhesionstrength were determined at room temperature (i.e., 23° C.) as well asoccasionally at 70° and 100° C. Specimens were allowed 15 minutes topreheat prior to testing at elevated temperatures.

8. Adhesion strength is defined as:

peel adhesion strength (lbs./inch)=pounds force×sample width;

shear adhesion strength (lbs./square inch)=pounds force×sample width.

A number of test specimens were prepared for testing using the 5 gallonpail liner. First, a 9 to 10 mil film of the liner was prepared byheating the pail liner between Mylar film in a positive pressure mold.The resulting 10 mil film was inserted between two layers of rubber andpressed in a 6×6 inch positive pressure mold for about 5 minutes at 149°C. The pail liner has a peak melt temperature of about 129° C. to 130°C.

Rubber test pads were prepared in a positive pressure mold using about138.8 lbs/in² and about 13.9 lbs/in² on the 6×6 inch rubber test pad.All Instron testing was conducted using a crosshead and chart speed of 2ipm. All one inch wide test specimens were preheated for 15 minutes whentested at an elevated temperature.

Table III below shows a comparison of peel adhesion properties of roofcovering obtained using the thermoplastic films of Table I inconjunction with the sheeting of Table II and roof covering obtainedusing a regular adhesive (Example No. 1) and the sheeting of Table II.Roof sheeting formed from the compositions shown in Table II mayoptionally be scrim reinforced. Table IV shows a comparison of peeladhesion properties at elevated temperatures. Table V shows the samecomparison for shear adhesion properties.

In the examples illustrated in Tables III, IV and V, the controladhesive used was the commercially available lap splice adhesiveUniroyal SA-1065, a butyl based lap splice adhesive for EPDM roof sheetmaterials. The composition of the EPDM sheeting used in Table III isprovided in Table II.

                                      TABLE III                                   __________________________________________________________________________    ROOM TEMPERATURE PEEL ADHESION COMPARISON                                     Ex. No.                                                                            Type of Adhesive/Film                                                                     Properties Measured                                                                      Adhesion Results/Seam Failures                    __________________________________________________________________________    1    Adhesive    Peel Adhesion,                                                                           1-7                                                    Seamed      lbs/inch   Adhesive Failure                                       Control(a)  Seam Failure                                                                             Type of Sheeting                                                              EPDM (I)                                                                             EPDM (II)                                                                            EPDM (III)                                                      Sulfur Cured                                                                         Sulfur Cured                                                                         Uncured                                                         Scrim  Unreinforced                                                                         Scrim                                                           Reinforced    Reinforced                          2    RED PE      Peel Adhesion,                                                                           0.6-1.6                                                                                3-5.4                                                                              0.8                                      liner       lbs/inch   (A)    (A), (B)                                                                             (A)                                                  Seam Failure                                                 3    Transparent Peel Adhesion,                                                                           0.6-2.2                                                                              2.8-7  2.2-4                                    PE liner    lbs/inch   (A)    (A), (B)                                                                             (A)                                                  Seam Failure                                                 4    Embossed    Peel Adhesion,                                                                           1-2    3-4    0.8-1                                    PE liner    lbs/inch   (A)    (A), (B)                                                                             (A)                                                  Seam Failure                                                 5    5 gal.      Peel Adhesion,                                                                           2.3    >14.3  >15.6                                    pail liner  lbs/inch   (A)    (C)    (C)                                      (HDPE)      Seam Failure                                                 6    High MW                                                                       PE film                                                                       (a) P150 (6 mils)                                                                         Peel Adhesion,                                                                           .sup. 2.5.sup.b                                                                      .sup. >21.5.sup.b                                                                    .sup. >46.5.sup.b                                    lbs/inch   (A)    (C)    (C)                                                  Seam Failure                                                      (b) P550 (20 mils)                                                                        Peel Adhesion,                                                                           .sup.  .sup. >22.sup.b                                                                      .sup. >33.sup.b                                      lbs/inch   (A)    (C)    (C)                                                  Seam Failure                                                 __________________________________________________________________________     (A) = Failure occurred between thermoplastic film and rubber membrane         (B) = Tearing into the thermoplastic film itself                              (C) = Test specimen broke in Instron clamp or rubber tore to fabric           reinforcement during testing                                                  .sup.a Unreinforced, sulfur cured conventional black EPDM membrane seamed     with SA1065 lap splice adhesive                                               .sup.b Pressure during molding 138.8 psi                                 

                                      TABLE IV                                    __________________________________________________________________________    ELEVATED TEMPERATURE PEEL ADHESION COMPARISON                                 Ex. No.                                                                            Type of Adhesive/Film                                                                     Properties Measured                                                                       Adhesion Results/Seam Failures                   __________________________________________________________________________    1    Adhesive    Peel Adhesion @ 23° C.,                                                            1-7                                                   Seamed      lbs/inch    Adhesive Failure                                      Control.sup.a                                                                             Seam Failure                                                 7    Adhesive    Peel Adhesion @ 70° C.,                                                            1.2                                                   Seamed      lbs/inch    Adhesive Failure                                      Control.sup.a                                                                             Seam Failure                                                 8    Adhesive    Peel Adhesion @ 100° C.,                                                            0.85                                                 Seamed      lbs/inch    Adhesive Failure                                      Control.sup.a                                                                             Seam Failure                                                                              Type of Sheeting                                                              Reinforced                                                                           Unreinforced                                                                         Reinforced                                                      Sulfur Cured                                                                         Sulfur Cured                                                                         Uncured                                                         EPDM (I)                                                                             EPDM (II)                                                                            EPDM (III)                         9    5 gal. pail liner                                                                         Peel Adhesion at 23 ° C.,                                                          --     >23.5.sup.c                                                                          >34.sup.c                               (HDPE)      lbs/inch    --     (C)    (C)                                                 Seam Failure                                                 10   5 gal. pail liner                                                                         Peel Adhesion @ 70° C.,                                                            --     >20.sup.c                                                                            >2.1.sup.c                                          lbs/inch    --     (C)    (C)                                                 Seam Failure                                                 11   5 gal. pail liner                                                                         Peel Adhesion @ 100° C.,                                                           --     >14.4.sup.c                                                                          >1.7.sup.c                              (HDPE)      lbs/inch    --     (C)    (C)                                                 Seam Failure                                                 12   High MW                                                                       PE Film                                                                       (a) P150 (6 mils)                                                                         Peel Adhesion @ 70° C.,                                                            1      >12.5.sup.b                                                                          >2.2.sup.b                                          lbs/inch    (A)    (C)    (C)                                                 Seam Failure                                                      (b) P550 (20 mils)                                                                        Peel Adhesion @ 70° C.,                                                            2.5-3  >14.sup.b                                                                            >2.65.sup.b                                         lbs/inch    (A)    (C)    (C)                                                 Seam Failure                                                 __________________________________________________________________________     (A) = Failure occurred between thermoplastic film and rubber membrane         (B) = Tearing into the thermoplastic film itself                              (C) = Test specimen broke in Instron clamp or rubber tore to fabric           reinforcement during testing                                                  .sup.a Unreinforced sulfur cured conventional black EPDM membrane seamed      with SA1065 lap splice adhesive                                               .sup.b Pressure during molding 138.8 psi                                      .sup.c Pressure during molding 13.9 psi                                  

                                      TABLE V                                     __________________________________________________________________________    SHEAR STRENGTH COMPARISON                                                     Ex. No.                                                                            Type of Adhesive/Film                                                                     Properties Measured                                                                          Adhesion Results/Seam Failures                __________________________________________________________________________    13   Adhesive Seamed                                                                           Seam Shear Strength @ 23° C.,                                                         27                                                 Control.sup.a                                                                             lbs/inch.sup.2 Adhesive Failure                                               Seam Failure                                                 14   Adhesive Seamed                                                                           Seam Shear Strength @ 70° C.,                                                         11.5                                               Control.sup.a                                                                             lbs/inch.sup.2 Adhesive Failure                                               Seam Failure   Type of Sheeting                                                              Reinforced                                                                           Unreinforced                                                                         Reinforced                                                      Sulfur Cured                                                                         Sulfur Cured                                                                         Uncured                                                         EPDM (I)                                                                             EPDM (II)                                                                            EPDM (III)                      15   5 gal. pail liner                                                                         Seam Shear Strength @ 23° C.,                                                         --     >27.5  --                                               lbs/inch.sup.2 --     (C)    --                                               Seam Failure                                                 16   5 gal. pail liner                                                                         Seam Shear Strength @ 70° C.,                                                         --     >21.5  --                                               lbs/inch.sup.2 --     (C)    --                                               Seam Failure                                                 __________________________________________________________________________     (C) = Test specimen broke in Instron clamp or rubber tore to fabric           reinforcement during testing                                                  .sup.a Unreinforced sulfur cured conventional black EPDM membrane seamed      with SA1065 lap splice adhesive                                          

Peel adhesion as shown in Table III for the adhesive seamed conventionalblack EPDM membrane (control) at 23° C. was 1-7 lbs/inch, while seamshear adhesion at 23° C. in Table V was 27 lbs/square inch. The controladhesion test samples were prepared using an unreinforced sulfur curedconventional black EPDM membrane seamed with SA-1065, a lap spliceadhesive commercially available from Uniroyal Chemical. A substantialincrease in both peel and shear adhesion resulted using either theunreinforced, sulfur cured EPDM (II) sheeting or the reinforced, uncuredEPDM (III) sheet seamed with the HDPE (pail liner) or the ultra high MWpolyethylene (P150/P550) relative to the adhesive seamed control. Boththe sulfur cured and uncured black EPDM (I-III) sheets were seamed withthe polyethylene liners and gave comparable and/or directionallyimproved seam peel adhesion results. These adhesion results demonstratethat the use of polyethylene films such as those comprising polyethyleneand using sufficient heat and some pressure allows the formation ofacceptable seams without using adhesives. None of the experimental seamswere wash or scrubbed with gasoline or organic solvents during seampreparation.

In conclusion, it should be clear from the foregoing examples andspecification disclosure that the use of a thermoplastic film inconjunction with flat sheets featuring sulfur cured or uncured EPDM, EPRor other olefin type polymers allows such sheet material to be seamedalong the overlapped edges, using sufficient heat and some pressure,without the use of adhesives. Moreover, the sheet materials may notrequire that a dusting or release agent be applied to the surface of themembrane followed by autoclave curing. Also, roof sheeting materialformed from the formulations shown in Table II may optionally be scrimreinforced. It is to be understood that the invention is not limited tothe specific types of thermoplastic films or EPDM exemplified herein orby the disclosure of other typical EPDM, EPR or other olefin typepolymers provided herein, the examples having been provided merely todemonstrate the practice of the subject invention. Those skilled in theart may readily select other thermoplastic films, or other EPDM, EPR orother similar olefin polymers including copolymers of ethylene andbutene and ethylene and octene, according to the disclosure madehereinabove. Similarly, the invention is not necessarily limited to theparticular fillers and processing material exemplified or the amountsthereof.

Thus, it is believed that any of the variables disclosed herein canreadily be determined and controlled without departing from the scope ofthe invention herein disclosed and described. Moreover, the scope of theinvention shall include all modifications and variations that fallwithin the scope of the attached claims.

What is claimed is:
 1. A laminate seam of flat rubber heat seamable roofing sheet material comprising:two layers of said sheet material, at least one layer of which is uncured; and one layer of a thermoplastic film interposed between the edge area of said two layers of sheet material when said edge areas are overlapped to form a seam without the use of an adhesive; said sheet material consisting of a polymeric composition of matter consisting essentially of a semi-crystalline polyolefin rubber having more than about 2 percent by weight crystallinity and an ethylene content in excess of 60 percent, selected from the group consisting of ethylene-propylene copolymers and terpolymers; from about 20 to 300 parts by weight of a filler selected from the group consisting of reinforcing and non-reinforcing materials and mixtures thereof, per 100 parts of said polymer said roofing sheet material exhibiting a seam peel adhesion value of at least about 2 pounds/inch and a shear adhesion value of at least about 15 pounds/square inch, in the absence of adhesive, and from about 20 to 150 parts by weight of a processing material and mixtures thereof, per 100 parts of said polymer; wherein said seam is formed by application of heat and pressure at said edge areas for up to about 5 minutes.
 2. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said film is selected from the group consisting of polyolefins prepared from monomers having from about 2 to 8 carbon atoms, ethylene-vinyl acetate copolymers and blends thereof.
 3. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said polyolefin rubber comprises EPDM having an ethylene content of about 75 percent by weight and a weight average molecular weight of about 190,000.
 4. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said filler comprises about 110 parts by weight of carbon black and said composition of matter includes about 70 parts by weight of processing oil, per 100 parts of said polyolefin rubber.
 5. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said polyolefin rubber comprises EPDM having an ethylene content of about 60 percent by weight and a weight average molecular weight of about 360,000.
 6. A laminate seam of flat rubber sheet material, as set forth in claim 5, wherein said filler comprises about 110 parts by weight of carbon black and said composition of matter includes about 70 parts by weight of processing oil, per 100 parts of said polyolefin rubber.
 7. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said polyolefin rubber comprises EPDM having an ethylene content of about 67 percent by weight and a weight average molecular weight of about 313,000 to 355,000.
 8. A laminate seam of flat rubber sheet material, as set forth in claim 7, wherein said filler comprises about 110 parts by weight of carbon black and said composition of matter includes about 70 parts by weight of processing oil, per 100 parts of said polyolefin rubber.
 9. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said flat rubber sheet material is scrim-reinforced.
 10. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said flat rubber sheet material is unreinforced.
 11. A laminate seam of flat rubber sheet material, as set forth in claim 1, wherein said thermoplastic film has a thickness of from about 2 to 20 mils.
 12. A laminate seam of flat rubber heat seamable roofing sheet material comprising:two layers of said sheet material, at least one layer of which is uncured; and one layer of a thermoplastic film interposed between the edge area of said two layers of said sheet material when said edge areas are overlapped to form a seam without the use of an adhesive said sheet material consisting of a polymeric composition of matter consisting essentially of a semi-crystalline polyolefin rubber having more than about 2 percent by weight crystallinity and an ethylene content in excess of 60 percent, selected from the group consisting of ethylene-propylene copolymer and terpolymers, from about 20 to 300 parts by weight of a filler selected from the group consisting of reinforcing and non-reinforcing materials and mixtures thereof, per 100 parts of said polymer, and from about 20 to 150 parts by weight of a processing material and mixtures thereof, per 100 parts of said polymer; said roofing sheet material exhibiting a seam peel adhesion value of at least about 2 pounds/inch and a shear adhesion value of at least about 15 pounds/square inch, in the absence of adhesive. 